The Transportation Security Administration on Thursday unveiled body scanners at Logan International Airport that show only a generic outline instead of a slightly blurred image of a passenger’s naked body — fat rolls included.

The new image is a rudimentary, gender­neutral figure with mitten hands, a halo of hair, and no nose — a marked contrast to the photo-negative-like pictures that are so explicit they are viewed in private rooms by TSA officers.

Twenty-seven new machines that use electromagnetic waves instead of X-rays will replace all 17 of the older scanners, which have been used at Logan since 2010.

The new machines will project an identical “Gumby-type” image for each person, detecting weapons and other nonmetallic materials­ without actually showing the passenger’s body, TSA officials said. Both TSA screeners and passengers will be able to see the images at checkpoints.

“It’s just a continuation of the upgrading of our technology,” said George Naccara, the TSA’s security director at Logan.

The body scanners generated controversy when they were introduced at Logan and other airports, raising concerns about privacy and leading some passengers to arrive at checkpoints in their underwear in protest.

Privacy advocates have concerns about the new machines, however.

The Electronic Privacy Information Center, based in Washington, is moving ahead with a lawsuit over the body scanners. It was filed against the Department of Homeland Security, which oversees the TSA, in part because the latest versions of the device are still able to record and store images of passengers, said EPIC’s executive director, Marc Rotenberg.

Privacy advocates say those images could fall into the wrong hands.

The TSA said the scanners are manufactured with the ability to record images of passengers, but this function is disabled before they are installed in airports.

The TSA also has failed to show that the body scanners have detected threats that would not have been picked up by metal detectors, Rotenberg said, adding that several European airports have removed body scanners because they were ineffective.

The machines also need an outside evaluation to show they don’t pose a health risk, he said.

Rotenberg conceded the new machines are an improvement over the old ones.

“At least we don’t have government officials in dark rooms looking at naked air travelers — or at least the number is dropping,” he said.

The new devices produce no radiation, Naccara said.

Some passengers have opted to get a pat down instead of going through the scanners because of concerns about exposure to radiation.

DAVID L. RYAN/GLOBE STAFF

The TSA says new machines won’t store images.

Peggy Bunker, 65, of Ashland, went through one of the new scanners at Logan Airport on Thursday, on her way to watch her daughter run a half-marathon in Long Beach, Calif. Bunker said she did not mind the more revealing images on the old machine — “It really doesn’t faze me at this age” — but acknowledgedmost people would probably prefer the new system.

“It’s better for a lot of people that really objected to the other one,” she said.

The scanner did detect her driver’s license and boarding pass, which she had tucked into her bra, and she was pulled aside for a pat down.

The new scanners generate an image only if they detect an anomaly, such as a powdered explosive — or a boarding pass tucked in a bra. If nothing is found, the word “OK” appears on the screen. The process will also be quicker, Naccara said, taking three to five seconds instead of the 16 to 18 seconds the old machines required.

In all, the TSA has installed 730 body scanners at more than 190 airports around the country, 555 of which use the new software with the generic body outline.

At Logan, the machines will be installed at each of the airport’s 10 checkpoints by mid-November. Eventually, Naccara said, fewer machines will be needed as more travelers enroll in the TSA’s expedited screening program, which allows prescreened frequent fliers to go through separate security lanes without removing their shoes or showing gels and liquids.